1. Field of the Invention
The present invention relates to a lens holder for holding an objective lens used in an optical pickup head in an optical disk apparatus such as a compact disk (CD) player or a laser disk (LD) player.
2. Description of the Related Art
Conventionally, optical disk apparatuses such as compact disk (CD) players and laser disk (LD) players have been put to practical use. As is well known, an optical disk apparatus is so arranged that a laser beam (hereafter simply referred to as the beam) emitted from a laser diode is focused by an objective lens (hereafter simply referred to as the lens) and is radiated to an optical disk, and the reflected light from the disk is detected by a sensor (PIN photodiode), to as to read information recorded on the surface of the optical disk irradiated by the beam.
Incidentally, with respect to the optical disk which is rotated at a high speed, the lens is moved at a high speed to apply the beam emitted from the laser diode to a proper position (reading position) on the optical disk, and the gravitational acceleration which is momentarily very large can be applied to the lens. Accordingly, unless the lens is firmly secured to the lens holder, problems occur in which the position where the lens is fixed to the lens holder becomes offset or the lens becomes disengaged from the lens holder.
In addition, a lens using an acrylic synthetic resin as a raw material tends to be used for the purpose of reducing the cost of the apparatus itself. With this type of lens, since the mechanical strength of the raw material is weaker than a lens using glass as a raw material, an adhesive agent is used for fixing the lens to the lens holder. In addition, various techniques have been proposed to fix the lens to the lens holder with sufficient strength (such as JP-B-8-329508 and JP-A-9-35312).
With the conventionally proposed techniques, a recessed portion capable of retaining an adhesive agent is formed in an outer wall surrounding a side surface of the lens inserted in a lens insertion hole formed in the lens holder. Since the adhesive agent is thus poured into the recessed portion formed in the outer wall portion, the adhesive agent poured into the recessed portion adheres in a large amount to the side surface of the lens inserted in the insertion hole, thereby improving the strength of adhesive bonding of the lens to the lens holder.
However, there has been a problem in that when the lens is bonded and secured to the lens holder, the adhesive agent poured in the recessed portion overflows from the recessed portion, and the overflowing adhesive agent flows to the insertion hole side of the lens holder and adheres to the surface of the lens inserted in the insertion hole. It should be noted that, if the adhesive agent adheres to the lens surface, the aberrations of the lens deteriorate, and it becomes impossible to focus the beam emitted from the laser diode to a sufficient size. Accordingly, the accuracy for reading the information recorded on the optical disk declines.
For this reason, a huge outer ring (a peripheral annular wall on the outer side of the effective diameter of the lens) is conventionally provided on an outer periphery of the lens so ensure the adhesive agent overflowing from the recessed portion does not adhere to the huge outer ring and does not adhere to the lens surface. Incidentally, in this case, since the outside diameter of the lens becomes large, there is a problem in that the lens holder becomes large in size.
In addition, although proposals are made in JP-B-8-329508 and JP-A-9-35312 to newly provide a recessed portion for receiving the adhesive agent overflowing from the recessed portion to the insertion hole side, a sufficient effect is not thereby obtained.
The present invention has been made in view of the above, and therefore an object of this invention is to provide a lens holder which makes it possible to obtain sufficient strength in the attachment of the lens by using an adhesive agent and which makes it possible to prevent the adhesive agent from adhering to the lens surface, by adopting a shape allowing the overflowing adhesive agent to flow to the outer side of the lens holder in view of the fact that the cause of the aforementioned problems lies in the fact that the overflowing adhesive agent flows to the insertion hole side.
To achieve the above object, the lens holder in accordance with the invention has the following features:
(1) A lens holder for fixing a lens thereto by using an adhesive agent, wherein an insertion hole for insertion of the lens, a lens receiving portion for receiving the lens inserted in the insertion hole, and an outer wall portion for surrounding a side surface of the lens inserted in the insertion hole and received by the lens receiving portion are formed, and a plurality of slots into which the adhesive agent is poured and which are adapted to fix the lens inserted in the insertion hole are formed in the outer wall portion, the slots being formed in a shape for dividing the outer wall portion.
(2) The slots have a shape in which bottom surfaces thereof are located upwardly of the lens receiving portion.
(3) The bottom surfaces of the slots are inclined surfaces which are inclined toward an outer side of the lens holder.
(4) The bottom surfaces of the slots are chevron-shaped surfaces in which inclined surfaces which are inclined to an inner side and an outer side of the lens holder are made to abut against each other.
In this construction, the lens inserted in the insertion hole is bonded and secured by the adhesive agent poured in the slots at portions corresponding to the slots formed in the outer wall portion. Accordingly, since a sufficient amount of adhesive agent can be allowed to adhere to the lens, the lens can be fixed to the lens holder with sufficient strength. In addition, since the outer sides of the slots are open, the adhesive agent overflowing from the slots overflows not only to the inner side of the slots, i.e., to the insertion hole side, but also to the outer side of the slots. Accordingly, it is possible to reduce the amount of adhesive agent flowing into the insertion hole side, and it is possible to effectively prevent the adhesive agent from adhering to the lens surface.
In addition, since the bottom surfaces of the slots are located upwardly of the lens receiving portion, the adhesive agent flowing into the insertion hole side from the slots enters the gap between the outer peripheral surface of the lens inserted in the insertion hole and the inner peripheral surface of the lens holder. Accordingly, it is possible to bond and secure the lens to the lens holder more firmly.
In addition, if the bottom surfaces of the slots are formed as inclined surfaces which are inclined to the outer side, it is possible to further reduce the amount of adhesive agent flowing into the insertion hole side, and it is possible to substantially reliably prevent the adhesive agent from adhering to the lens surface.
In addition, if the bottom surfaces of the slots are formed in chevron shapes, it is possible to allow an appropriate amount of adhesive agent to flow into the insertion hole side as well. Hence, the adhesive agent can be allowed to enter the gap between the outer peripheral surface of the lens inserted in the insertion hole and the inner peripheral surface of the lens holder, so that it is possible to bond and secure the lens to the lens holder even more firmly.